The development of dopamine D2-receptor selective antagonists

Area of Science:

• Medicinal Chemistry
• Neuropharmacology
• Radioligand Development

Background:

• Benzamides, including remoxipride and salicylamides like raclopride, have been foundational in dopamine D2 receptor research.
• Structural modifications led to 5,6-dioxygenated benzamide moieties with altered receptor binding properties.

Purpose of the Study:

• To review the development of 2,6- and 5,6-dioxygenated benzamides.
• To discuss structure-activity relationships, conformational, and stereochemical aspects.
• To highlight their utility as selective dopamine D2 receptor antagonists and radioligands.

Main Methods:

• Review of structure-activity relationships (SAR) for benzamide derivatives.
• Analysis of conformational and stereochemical requirements for receptor binding.
• Evaluation of in vitro and in vivo potency and selectivity.

Main Results:

• Different side chain classes ((S)-2-pyrrolidinylmethyl-, (R)-2-pyrrolidinylmethyl-, 4-piperidinylbenzamides) exhibit distinct aromatic substituent and side chain conformation needs.
• Lipophilic nitrogen substituents are crucial for dopamine D2 receptor affinity in certain benzamide classes.
• 3-substituted 5,6-dimethoxysalicylamides and 5,6-dimethoxybenzamides are highly potent and selective dopamine D2 antagonists.

Conclusions:

• The studied benzamides possess unique pharmacophoric requirements, aiding in dopamine D2 receptor subtype investigations.
• Developed radioligands (e.g., NCQ 298, FLB 457) are suitable for receptor binding assays, PET, and SPECT imaging.
• These selective ligands facilitate further characterization of dopamine D2 receptors and related responses.